A. Field of the Invention
This invention relates generally to industrial and commercial blast freezing systems for comestibles such as meat, seafood, vegetables and baked products. In particular, the invention relates to a blast freezer system designed for continuous production and which achieves a high throughput of product with a minimum of labor. The freezer system can be either fixed or portable. Some embodiments described below are particularly suited for installation on fishing boats or in remote processing locations, but the invention is applicable to freezing systems in general.
B. Description of Related Art
Many methods are commonly used for preserving foodstuffs, including canning, salting, drying, retort pouching, smoking and freezing. However, all of these methods substantially alter the taste and texture of the preserved foodstuff that typify freshness, except freezing. Freezing can maintain the freshness of food, medical specimens and other items for extended periods of time and can be considered the preferred method of long term preservation for almost all foodstuffs, particularly seafood, meat, fruit and vegetables as well as baked goods. Blast freezing systems are known which are designed for freezing large quantities of comestibles such as meats, seafood, vegetables and bakery products, in a relatively short amount of time. Such systems work by subjecting the comestibles to air, moving at high velocity, chilled to very low temperatures, such as −40 degrees F., for a period of time sufficient to completely freeze the product.
The process of freezing unavoidably changes the food product chemically, biologically and physically. The magnitude of these changes, and the resulting quality of the frozen food product, is greatly affected by many factors, including the rate, method and temperature of the freezing process, and the temperature and air velocity during freezing and storage. Generally speaking, it is accepted that fast freezing rates and low consistent storage temperatures are necessary for high quality in most frozen food products. Fast freezing rates create smaller ice crystal formation and less migration of compounds that remain soluble during the freezing process, which greatly affects the taste and texture of the resulting frozen product. Depending on the type of foodstuff, some compounds continue to migrate after the product is considered frozen, further altering the taste and texture. Although recommended storage temperature very for different products, consistent low temperatures of −20° F. to −40° F. or lower reduce this migration to nil and are considered necessary for the high quality long term storage of most frozen food. So-called blast freezing systems have been developed to freeze foodstuffs at these temperatures quickly.
Another factor that greatly affects the quality of frozen foodstuff and other items is the elapsed time between harvesting and freezing. Most products, particularly seafood, begin to deteriorate rapidly after harvest, resulting in altered taste and texture making them less desirable in the market place. Fishing vessels, in order to sell to more particular markets and to stay on the fishing ground until full, must have suitable production equipment on board for freezing while at sea. Likewise, agricultural organizations must have production freezing equipment nearby, reducing the time between harvest and processing making the resulting product suitable for the more desirable markets that expect high quality frozen foods.
Freezing methods and systems are described in U.S. Pat. Nos. 6,235,332, 4,164,129, 5,452,588, 3,696,631, and 4,164,129. A ship-board freezing system is set forth in U.S. Pat. No. 3,696,631. This patent relates to brine freezing onboard a fishing vessel, specifically a deck mounted brine freezing apparatus and integral hold refrigeration system. Brine freezing is often used for shrimp and other similar product and is accomplished at warmer temperatures than desirable for many other freezing applications. While the system of the '631 patent may be well suited for its intended purpose of brine freezing shrimp, it is not suited for broad use on a variety of different comestibles. Other prior art of interest includes British patent GB 1,369,093 and U.S. Pat. No. 6,009,719. My prior U.S. Pat. No. 6,796,142 discloses a continuous throughput blast freezer system which overcomes many of the limitations of the above prior art. The entire content of my prior '142 patent is incorporated by reference herein.
The world-wide expansion and globalization of food producing entities has greatly increased the need for versatile production freezing equipment that can produce very high quality products, suitable for installation onboard fishing vessels, processing vessels and land based installations in remote areas of the world, as well as more conventional plant locations near industrial centers. Another desirable feature is for the freezing system to be containerized and or modular, suitable for manufacturing complete or near complete at the factory enabling easy shipment and commissioning at a remote site. Another desirable feature is for the freezing system to be portable, suitable for moving to new areas as individual fish run seasons are completed, or the harvest of one crop is completed and the freezing capacity is needed elsewhere. Production freezing equipment represents a major investment for most organizations and is therefore important for the equipment to be versatile and suitable for a wide variety of products.
This invention relates to an improved continuous throughput blast freezer system which provides still further improvements and efficiencies over the known prior art. While some of the features of the preferred embodiment are specifically designed and adapted for use in a mobile, i.e., portable, freezer application, others features of the disclosed embodiments are capable of employment in freezer systems generally, as will be apparent from the following discussion. One advantage of the system of this disclosure is that it provides a compact arrangement for freezing large amounts of comestibles, for example as compared to so-called “spiral” freezers such as shown in U.S. Pat. No. 4,164,129.